snaptool should not allow live edits to config file via web page by default

[kirkwatrous]

By default since v1.6, snaptool now allows anyone hitting the web page to make live edits to the config file, no authentication even required. This can be disabled via the --no-edit command-line argument, but that is arguably a dangerous default! Why not reverse this behaviour: do not allow unauthenticated edits by default, and only enable this behaviour when explicitly asked for, such as with a different command-line argument (--edit, --allow-edit or some such).